A major goal for HIV-1 vaccine development is an ability to elicit strong and durable broadly neutralizing antibody (bNAb) responses. The trimeric envelope glycoprotein (Env) spikes on HIV-1 are known to contain multiple epitopes that are susceptible to bNAbs isolated from infected individuals. Nonetheless, all trimeric and monomeric Env immunogens designed to date have failed to elicit such antibodies. We report the structure-guided design of HIV-1 cyclically permuted gp120 that forms homogeneous, stable trimers, and displays enhanced binding to multiple bNAbs, including VRC01, VRC03, VRC-PG04, PGT128, and the quaternary epitope-specific bNAbs PGT145 and PGDM1400. Constructs that were cyclically permuted in the V1 loop region and contained an N-terminal trimerization domain to stabilize V1V2-mediated quaternary interactions, showed the highest homogeneity and the best antigenic characteristics. In guinea pigs, a DNA prime-protein boost regimen with these new gp120 trimer immunogens elicited potent neutralizing antibody responses against highly sensitive Tier 1A isolates and weaker neutralizing antibody responses with an average titer of about 115 against a panel of heterologous Tier 2 isolates. A modest fraction of the Tier 2 virus neutralizing activity appeared to target the CD4 binding site on gp120. These results suggest that cyclically permuted HIV-1 gp120 trimers represent a viable platform in which further modifications may be made to eventually achieve protective bNAb responses.The HIV-1 Env displayed on the virion surface mediates entry of the virion into target CD4 ϩ T cells to establish infection. Due to its surface accessibility, Env is the predominant target for neutralizing antibody responses (1, 2). Env is synthesized as a gp160 precursor protein, which is further cleaved into surface proximal gp120 and membrane anchored gp41 subunits. A functional HIV-1 Env spike consists of a trimer of gp120 and gp41 heterodimers. The base of the trimer is proximal to the viral membrane (3) and is held together by trimerization motifs within the N-heptad repeat of gp41 (4 -6). The trimer apex is stabilized by interactions between the V1V2 loops of adjacent gp120 monomers (3). Binding of Env to the CD4 receptor on T cells causes extensive conformational changes in the Env trimer and leads to the formation of an open CD4-bound conformation in which the cryptic, co-receptor binding site becomes accessible. This facilitates interaction of the co-receptor (CCR5 or CXCR4) with Env, further driving the fusion of viral and host cell membranes (3, 7).In natural HIV-1 infection, most of the B cell response is elicited against the Env protein, due to its location on the virion surface and relatively high immunogenicity. The antibody response induced during natural HIV-1 infection is predominantly non-neutralizing and strain specific, due to the shed gp120 (immunodominant decoys) and various other immune evasive mechanisms (8). However, ϳ20% of HIV-1-infected patients develop bNAbs during the course of 1-3 years of infectio...
DNA processing protein A (DprA) plays a crucial role in the process of natural transformation. This is accomplished through binding and subsequent protection of incoming foreign DNA during the process of internalization. DprA along with Single stranded DNA binding protein A (SsbA) acts as an accessory factor for RecA mediated DNA strand exchange. H. pylori DprA (HpDprA) is divided into an N-terminal domain and a C- terminal domain. In the present study, individual domains of HpDprA have been characterized for their ability to bind single stranded (ssDNA) and double stranded DNA (dsDNA). Oligomeric studies revealed that HpDprA possesses two sites for dimerization which enables HpDprA to form large and tightly packed complexes with ss and dsDNA. While the N-terminal domain was found to be sufficient for binding with ss or ds DNA, C-terminal domain has an important role in the assembly of poly-nucleoprotein complex. Using site directed mutagenesis approach, we show that a pocket comprising positively charged amino acids in the N-terminal domain has an important role in the binding of ss and dsDNA. Together, a functional cross talk between the two domains of HpDprA facilitating the binding and formation of higher order complex with DNA is discussed.
To study the effect of reinforcement type and quantity on the response of model slopes in this study, a series of shaking table tests were carried out on model slopes reinforced with different quantities of geotextile and geogrid. Model slopes were constructed to an angle of 45°using poorly graded sand. Acceleration of base shaking and shaking frequency were varied in different tests. The response of model soil slopes is compared in terms of the acceleration amplifications and horizontal displacements of the slope measured at different elevations. Results from these model tests revealed that the acceleration amplifications were slightly lesser in case of geogrid reinforced slopes because of higher interfacial friction of cohesionless soil with the geogrid. Acceleration amplifications were not affected by varying the quantity of reinforcement. However, horizontal displacements reduced drastically with the inclusion of reinforcement. Though the difference was not substantial, geotextile reinforced slopes were more effective in reducing the deformations compared to geogrid reinforced slopes. With the increase in the quantity of reinforcement, deformations decreased linearly, until reinforcement saturation occurred, beyond which the rate of decrease of deformations was less.
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